Geolocation refers to techniques for determining the geographic location of an object. Various types of geolocation exist. The present invention is applicable to environments where the object to be geolocated emits a signal. In such environments, various measurements can be performed on the received signal to estimate the location of the emitting object. For example, a receiver can perform angle (or direction) of arrival techniques to estimate the angle between the emitting object and the boresight vector of the antenna's receiver.
Angle of arrival techniques are often performed by detecting phase differences at a number of antennas that receive the signal emitted by the object. To detect the angle of arrival, the detected phase differences are compared to calculated phase differences (based on steering vectors) for each of a number of possible angles to identify which calculated phase differences most closely correlate with the detected phase differences. The angle that corresponds to the most closely correlated phase differences can then be identified as the angle of arrival of the received signal.
Because phase is cyclical, there may be instances where multiple sets of calculated phase differences closely correlate with the detected phase differences. In such instances, the angle of arrival calculations may yield multiple possible angles of arrival such that there would be ambiguity as to what the actual angle of arrival was. For example, a calculated phase difference corresponding to an incorrect angle of arrival may have a higher correlation than the calculated phase difference corresponding to the correct angle of arrival. Such ambiguity may be worsened in multipath environments since the phase of the multipath signal will interfere with the phase of the direct path signal.